Ventilatory function after exposure to various respirable hazards in a population of former coal miners.

The ventilatory function of 406 male former coal miners who had presented at the Cook County Hospital occupational medicine clinic between January 1976 and April 1987 was studied to determine whether subsequent exposure to respiratory hazards after leaving the coal mines adversely affected lung function. The miners were divided into five exposure groups based on their exposure to respirable hazards. These were coal dust only, coal dust plus asbestos dust, coal dust plus silica dust, coal dust plus another respirable hazard and coal dust plus two other respirable dust exposures. Duration of employment in coal mines, race, smoking history, and mean age were not significantly different between the various exposure groups. No significant difference was found in the per cent of predicted forced expiratory volume in one second (FEV1), per cent of predicted forced vital capacity (FVC), and FEV1/FVC when the coal dust only group was compared with each of the other four exposure groups using ANOVA. Among former coal miners who present for a respiratory disability determination, therefore, exposure to respirable hazards subsequent to employment in coal mines is not associated with a statistically significant deterioration in ventilatory function.     

Exposure-response relationships for coal mine dust and obstructive lung disease following enactment of the Federal Coal Mine Health and Safety Act of 1969.

Underground U.S. coal miners were studied cross-sectionally for the association of respirable coal mine dust exposure with pulmonary function and symptoms of airways obstruction. The study group included 1,185 miners participating in Round 4 of the National Study of Coal Workers' Pneumoconiosis who had started mining in or after 1970 when comprehensive exposure regulations first came into effect. Quantitative estimates of cumulative exposure, derived using respirable dust measurements taken by the Mine Safety and Health Administration over the entire study period, were used in linear and logistic regression models on indicators of pulmonary function and chest symptoms while controlling for smoking status, pack-years, and other potential confounders. Statistically significant associations between log cumulative exposure and decrements in FVC, FEV1, and FEV1/FVC were observed. In logistic models, statistically significant associations of cumulative exposure with increasing prevalence of FEV1 and FEV1/FVC less than 80% predicted and symptoms including chronic phlegm, chronic bronchitis, breathlessness, wheeze, and wheeze with shortness of breath were found. It is concluded that exposures to respirable coal mine dust present in U.S. mines since 1970 continue to affect respiratory health in underground miners.     

Differential respirable dust related lung function effects between current and former South African coal miners

Dust-related dose-response decrements in lung function among coal miners have been reported in several studies, with varying magnitudes across populations. Few studies have compared differences between current and former coal miners. No studies on dose response relationships with lung function have been conducted in South African coal mines, one of the top three producers of coal internationally. The objectives of this study were (1) to describe the relationship between respirable dust exposure and lung function among current and former South African coal miners and to determine whether differential dust related effects were present between these employment categories; (2) to examine dust related dose response relationships, controlling for potential confounding by smoking and a history of tuberculosis (TB). Six hundred and eighty-four current and 188 ex-miners from three bituminous coal mines in Mpumalanga Province were studied. Interviews assessing work histories, smoking profiles and other risk factors were conducted. Work histories were also obtained from company records. Standardised spirometry was performed by trained technicians. Cumulative respirable dust exposure (CDE) estimates were constructed from company-collected sampling and measurements conducted by the researchers. Regression models examined the associations of CDE with per cent predicted FEV₁ and FVC, controlling for smoking, past history of TB and employment status. A statistically significant decline in FEV₁ of 1.1 and 2.2 ml/mg-year/m³ was found in representative 40-year-old, 1.7-m tall current and former miners, respectively. Significant differences were found between the highest and medium exposure categories. Ex-miners had a lower mean per cent predicted lung function than current miners for each cumulative exposure category, suggesting a healthy worker effect. Past history of TB contributed to 21 and 14% declines in per cent predicted FEV₁ and FVC, respectively. Thus, in this cohort, a dose-related decline in lung function was associated with respirable dust exposure, with a magnitude of effect similar to that seen in other studies and important differences between current and former employees. A healthy worker effect may have attenuated the magnitude of this relationship. TB was a significant contributor to lung function loss.     

Dust exposure, respiratory symptoms, and longitudinal decline of lung function in young coal miners.

OBJECTIVES: To study the role of dust exposure on incidence of respiratory symptoms and decline of lung function in young coal miners. METHODS: The loss of lung function (forced vital capacity (FVC), forced expiratory volume in one second (FEV1), forced expiratory flow (MEF), carbon monoxide transfer factor (TLCO)) with time and the incidence of respiratory symptoms in 909 Sardinian coal miners (followed up between 1983 and 1993 with seven separate surveys) has been compared with the past and current individual exposures to respirable mixed coal dust. Multiple linear and logistic regression models were used simultaneously controlling for age, smoking, past occupational exposures, and other relevant covariates. RESULTS: According to the relatively low dust exposures experienced during the follow up few abnormal chest x ray films were detected. In the cross sectional analysis of initial data, significant associations between individual cumulative exposure to dust, decrements in FEV1 and MEFs, and increasing prevalence of respiratory symptoms were detected after allowing for the covariates included in the model. The yearly decline of FVC, FEV1, and single breath carbon monoxide transfer factor (TLCO/VA) was still significantly related to the individual exposure to dust experienced during the follow up, even after allowing for age, smoking, initial cumulative exposure to dust, and initial level of each functional variable. In logistic models, dust exposure was a significant predictor of the onset of respiratory symptoms besides age and smoking. CONCLUSIONS: The results show that even moderate exposures to mixed coal dust, as in our study, significantly affect lung function and incidence of symptoms of underground miners. Although the frequency of chest x ray examination might be fixed at every three or four years, yearly measurements of lung function (spirometry, MEFs, and TLCO) are recommended for evaluation of the respiratory risk from the coal mine environment to assess the need for further preventive interventions.     

Relation between dust exposure and lung function in miners and ex-miners

A sample of men working in the British coal industry in the 1950s has been followed up and examined 22 years later. The relations between lung function and individual cumulative exposure to respirable dust have been studied in 1867 men who were still working in the industry at the time of follow up and 2192 men who had left. Levels of forced expired volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio at follow up were found to be inversely related to exposure to respirable dust after allowing for other factors, even in men without pneumoconiosis. The magnitude of this estimated effect was equivalent to a loss of 228 ml FEV1 in response to an exposure of 300 gh/m3, a moderately high exposure for this group. Ex-miners aged under 65 had worse lung function than miners on average, suggesting that ill health had encouraged some of these men to leave the industry. Whereas a more severe response to dust exposure among ex-miners under 65 was suggested, this difference could easily have arisen by chance. The presence of symptoms of chronic bronchitis was associated with reduced levels of lung function, however, and, additionally, ex-miners under 65 with chronic bronchitis showed a more severe response of the FVC to dust exposure than miners without these symptoms. Among these ex-miners with chronic bronchitis a small group of men who had taken other jobs showed a much more severe effect of dust exposure on their lung function than the average, likely in heavily exposed men to contribute importantly to disability. Men in this group who had given up smoking showed and even more severe effect of dust exposure, equivalent to a loss of 940 ml FEV1 in response to an exposure of 300 gh/m3. These results indicate that exposure to respirable dust can occasionally cause severe respiratory impairment in the absence of progressive massive fibrosis. Dust exposure was related to a parallel reduction of FEV1 and FVC, implying that the pathology of dust induced lung damage differs form that induced by smoking. This pattern of abnormality was shown by some non-smokers, whereas smokers and ex-smokers apparently severely affected by dust showed a classic obstructive pattern of abnormality with pronounced reduction of the FEV1/FVC ratio.     

煤矿新工人早期肺通气功能的变化

目的　研究煤矿粉尘对新工人肺通气功能的早期影响。方法　选择徐州矿务集团新招收的男性工人2 87人为矿工组,选择该集团技工学校在校男生132人为对照组。调查内容包括个人基本资料、家族疾病史、职业史、吸烟史、作业场所粉尘浓度、肺通气功能随访测定。前瞻性队列调查为期3年,每半个月测定作业场所的总粉尘和呼吸性粉尘浓度;定期测定两组人群的用力肺活量(FVC)和第一秒用力呼气量(FEV1)。结果　矿工作业场所的总粉尘平均浓度为2 3.8mg/m3 ,呼吸性粉尘平均浓度为8.9mg/m3 ,均超过国家卫生标准。接尘第1年,矿工组FVC(5 .19L)高于对照组(4.92L) ,差异有统计学意义(P <0 .0 1) ,第2年和第3年的差异均无统计学意义(P >0 .0 5 )。接尘前矿工组FEV1[(4.4 8±0 .4 9)L]高于对照组[(4.2 8±0 .4 8)L];接尘1年时FEV1下降至4 .2 5L ;第2年和第3年FEV1(4.34L)低于对照组(4.5 6L) ,差异有统计学意义(P <0 .0 1)。矿工组FEV1呈下降趋势。矿工吸烟者3年中的FVC、FEV1损失量(15 4、184ml)高于不吸烟者(83、91ml)。FVC、FEV1与年龄、身高和体重存在一定相关。结论　粉尘对煤矿新工人的早期肺通气功能有明显影响,FEV1下降比FVC更为明显;吸烟可加重粉尘对肺通气功能的损害。     

Relation between dust exposure and lung function in miners and ex-miners.

A sample of men working in the British coal industry in the 1950s has been followed up and examined 22 years later. The relations between lung function and individual cumulative exposure to respirable dust have been studied in 1867 men who were still working in the industry at the time of follow up and 2192 men who had left. Levels of forced expired volume in one second (FEV1), forced vital capacity (FVC), and FEV1/FVC ratio at follow up were found to be inversely related to exposure to respirable dust after allowing for other factors, even in men without pneumoconiosis. The magnitude of this estimated effect was equivalent to a loss of 228 ml FEV1 in response to an exposure of 300 gh/m3, a moderately high exposure for this group. Ex-miners aged under 65 had worse lung function than miners on average, suggesting that ill health had encouraged some of these men to leave the industry. Whereas a more severe response to dust exposure among ex-miners under 65 was suggested, this difference could easily have arisen by chance. The presence of symptoms of chronic bronchitis was associated with reduced levels of lung function, however, and, additionally, ex-miners under 65 with chronic bronchitis showed a more severe response of the FVC to dust exposure than miners without these symptoms. Among these ex-miners with chronic bronchitis a small group of men who had taken other jobs showed a much more severe effect of dust exposure on their lung function than the average, likely in heavily exposed men to contribute importantly to disability. Men in this group who had given up smoking showed and even more severe effect of dust exposure, equivalent to a loss of 940 ml FEV1 in response to an exposure of 300 gh/m3. These results indicate that exposure to respirable dust can occasionally cause severe respiratory impairment in the absence of progressive massive fibrosis. Dust exposure was related to a parallel reduction of FEV1 and FVC, implying that the pathology of dust induced lung damage differs form that induced by smoking. This pattern of abnormality was shown by some non-smokers, whereas smokers and ex-smokers apparently severely affected by dust showed a classic obstructive pattern of abnormality with pronounced reduction of the FEV1/FVC ratio.     

Longitudinal and cross sectional analyses of exposure to coal mine dust and pulmonary function in new miners.

The association between exposure to dust and pulmonary function was studied by longitudinal and cross sectional analyses in a group of United States underground coal miners beginning work in or after 1970. Quantitative estimates of exposure to respirable coal mine dust were derived from air samples taken periodically over the entire study period. The cohort included 977 miners examined both in round 2 (R2) (1972-5) and round 4 (R4) (1985-8) of the National Study of Coal Workers' Pneumoconiosis. Multiple linear regression models were developed for both cross sectional (pulmonary function at R2 and R4) and longitudinal (change in pulmonary function between R2 and R4) analyses with exposure partitioned into pre-R2 and post-R2 periods and controlled for covariates including smoking history. The results indicate a rapid initial (at R2) loss of FVC and FEV1 in association with cumulative exposure of the order of 30 ml per mg/m3-years. Between R2 and R4 (about 13 years) no additional loss of function related to dust exposure was detected although the percentage of predicted FVC and FEV1 did decline over the period. After some 15 years since first exposure (at R4), a statistically significant association of cumulative exposure with FEV1 of about -5.9 ml per mg/m3-years was found. These results indicate a significant non-linear effect of exposure to dust on pulmonary function at dust concentrations present after regulations took effect. The initial responses in both the FVC and FEV1 are consistent with inflammation of the small airways in response to exposure to dust.     

A prospective cohort study among new Chinese coal miners: the early pattern of lung function change

Aims: To investigate the early pattern of longitudinal change in forced expiratory volume in 1 second (FEV1) among new Chinese coal miners, and the relation between coal mine dust exposure and the decline of lung function. Methods: The early pattern of lung function changes in 317 newly hired Chinese underground coal miners was compared to 132 referents. This three year prospective cohort study involved a pre-employment and 15 follow up health surveys, including a questionnaire and spirometry tests. Twice a month, total and respirable dust area sampling was done. The authors used a two stage analysis and a linear mixed effects model approach to analyse the longitudinal spirometry data, and to investigate the changes in FEV1 over time, controlling for age, height, pack years of smoking, mean respirable dust concentration, the room temperature during testing, and the groupxtime interaction terms. Results: FEV1 change over time in new miners is non-linear. New miners experience initial rapid FEV1 declines, primarily during the first year of mining, little change during the second year, and partial recovery during the third year. Both linear and quadratic time trends in FEV1 change are highly significant. Smoking miners lost more FEV1 than non-smokers. Referents, all age less than 20 years, showed continued lung growth, whereas the miners who were under age 20 exhibited a decline in FEV1. Conclusion: Dust and smoking affect lung function in young, newly hired Chinese coal miners. FEV1 change over the first three years of employment is non-linear. The findings have implications for both methods and interpretation of medical screening in coal mining and other dusty work: during the first several years of employment more frequent testing may be desirable, and caution is required in interpreting early FEV1 declines.     

Chronic respiratory effects of exposure to diesel emissions in coal mines

A 5-yr prospective design was employed to test the hypothesis that exposure to diesel emissions leads to chronic respiratory effects among underground coal miners. Changes in respiratory function and development of chronic respiratory symptoms were measured during a 5-yr study period (i.e., 1977 to 1982) in 280 diesel-exposed and 838 control miners from Eastern and Western United States underground coal mines. Spirometry measures of respiratory function included forced expiratory volume in 1 sec (FEV1.0), forced vital capacity (FVC), and forced expiratory flow rate at 50% of FVC (FEF50). Chronic respiratory symptom measures, which included chronic cough, chronic phlegm, and breathlessness, were obtained by questionnaires, as were smoking status and occupational history. Based upon these data, the pattern of evidence did not support the hypothesis either in an age-adjusted comparison of diesel vs. nondiesel miners or in an internal analysis by cumulative years of diesel exposure.     

Chronic Respiratory Effects of Exposure to Diesel Emissions in Coal Mines

A 5-yr prospective design was employed to test the hypothesis that exposure to diesel emissions leads to chronic respiratory effects among underground coal miners. Changes in respiratory function and development of chronic respiratory symptoms were measured during a 5-yr study period (i.e., 1977 to 1982) in 280 diesel-exposed and 838 control miners from Eastern and Western United States underground coal mines. Spirometry measures of respiratory function included forced expiratory volume in 1 sec (FEV, _1.0), forced vital capacity (FVC), and forced expiratory flow rate at 50% of FVC (FEF₅₀). Chronic respiratory symptom measures, which included chronic cough, chronic phlegm, and breathlessness, were obtained by questionnaires, as were smoking status and occupational history. Based upon these data, the pattern of evidence did not support the hypothesis either in an age-adjusted comparison of diesel vs. nondiesel miners or in an internal analysis by cumulative years of diesel exposure.     

Cement dust exposure and ventilatory function impairment: an exposure-response study

We investigated cumulative total cement dust exposure and ventilatory function impairment at a Portland cement factory in Tanzania. All 126 production workers were exposed. The control group comprised all 88 maintenance workers and 32 randomly chosen office workers. Exposed workers had significantly lower forced vital capacity (FVC), forced expiratory volume in 1 second (FEV1), peak expiratory flow rate (PEF), FEV1/FVC, FVC%, FEV1% and PEF%, than controls adjusted for age, duration of employment, height, and pack-years. Cumulative total dust exposure was significantly associated with reduced FVC, forced expiratory volume in 1 second, and peak expiratory flow rate adjusted for age, height and pack-years. Cumulative total dust exposure more than 300 mg/m year versus lower than 100 mg/m years was significantly associated with increased risk of developing airflow limitation (odds ratio = 9.9). The current occupational exposure limit for total cement dust (10 mg/m) appears to be too high to prevent respiratory health effects among cement workers.     

Work related decrement in pulmonary function in silicon carbide production workers.

The relation between pulmonary function, cigarette smoking, and exposure to mixed respirable dust containing silicon carbide (SiC), hydrocarbons, and small quantities of quartz, cristobalite, and graphite was evaluated in 156SiC production workers using linear regression models on the difference between measured and predicted FEV1 and FVC. Workers had an average of 16 (range 2-41) years of employment and 9.5 (range 0.6-39.7) mg-year/m3 cumulative respirable dust exposure; average dust exposure while employed was 0.63 (range 0.18-1.42) mg/m3. Occasional, low level (less than or equal to 1.5 ppm) sulphur dioxide (SO2) exposure also occurred. Significant decrements in FEV1 (8.2 ml; p less than 0.03) and FVC (9.4 ml; p less than 0.01) were related to each year of employment for the entire group. Never smokers lost 17.8 ml (p less than 0.02) of FEV1 and 17.0 (p less than 0.05) of FVC a year, whereas corresponding decrements of 9.1 ml (p = 0.12) in FEV1 and 14.4 ml (p less than 0.02) in FVC were found in current smokers. Similar losses in FEV1 and FVC were related to each mg-year/m3 of cumulative dust exposure for 138 workers with complete exposure information; these findings, however, were generally not significant owing to the smaller cohort and greater variability in this exposure measure. Never smokers had large decrements in FEV1 (40.7 ml; p less than 0.02) and FVC (32.9 ml; p = 0.08) per mg-year/m3 of cumulative dust exposure and non-significant decrements were found in current smokers (FEV1: -7.1 ml; FVC: -11.7 ml). A non-significant decrement in lung function was also related to average dust exposure while employed. No changes were associated with SO(2) exposure or and SO(2) dust interaction. These findings suggest that employment in SiC production is associated with an excessive decrement in pulmonary function and that current permissible exposure limits for dusts occurring in this industry may not adequately protect workers from developing chronic pulmonary disease.     

Work related decrement in pulmonary function in silicon carbide production workers

The relation between pulmonary function, cigarette smoking, and exposure to mixed respirable dust containing silicon carbide (SiC), hydrocarbons, and small quantities of quartz, cristobalite, and graphite was evaluated in 156SiC production workers using linear regression models on the difference between measured and predicted FEV1 and FVC. Workers had an average of 16 (range 2-41) years of employment and 9.5 (range 0.6-39.7) mg-year/m3 cumulative respirable dust exposure; average dust exposure while employed was 0.63 (range 0.18-1.42) mg/m3. Occasional, low level (less than or equal to 1.5 ppm) sulphur dioxide (SO2) exposure also occurred. Significant decrements in FEV1 (8.2 ml; p less than 0.03) and FVC (9.4 ml; p less than 0.01) were related to each year of employment for the entire group. Never smokers lost 17.8 ml (p less than 0.02) of FEV1 and 17.0 (p less than 0.05) of FVC a year, whereas corresponding decrements of 9.1 ml (p = 0.12) in FEV1 and 14.4 ml (p less than 0.02) in FVC were found in current smokers. Similar losses in FEV1 and FVC were related to each mg-year/m3 of cumulative dust exposure for 138 workers with complete exposure information; these findings, however, were generally not significant owing to the smaller cohort and greater variability in this exposure measure. Never smokers had large decrements in FEV1 (40.7 ml; p less than 0.02) and FVC (32.9 ml; p = 0.08) per mg-year/m3 of cumulative dust exposure and non-significant decrements were found in current smokers (FEV1: -7.1 ml; FVC: -11.7 ml). A non-significant decrement in lung function was also related to average dust exposure while employed. No changes were associated with SO(2) exposure or and SO(2) dust interaction. These findings suggest that employment in SiC production is associated with an excessive decrement in pulmonary function and that current permissible exposure limits for dusts occurring in this industry may not adequately protect workers from developing chronic pulmonary disease.     

An epidemiologic study of the respiratory effects of trona dust

Trona (sodium sesquicarbonate) is mined from an underground deposit in Wyoming and processed for use in glass, paper, detergent, and chemical applications. Trona dust is alkaline (pH 10.5) and can have an irritant effect on respiratory airways, mucous membranes, and the skin. A study population of 142 underground miners and 88 surface workers from one facility volunteered for an epidemiologic study. Their mean age was 37.6 yr and mean duration of employment was 10.0 yr. The percentage with chronic cough and phlegm was 23%; both symptoms were more common among smokers than nonsmokers. Thirty-three percent of the workers complained of dyspnea when hurrying on level ground or walking up a slight hill. Half of the workers complained of upper respiratory tract symptoms and eye irritation. Both smokers and exsmokers had significant declines of forced expiratory volume in 1 sec (FEV1.0) with age; exsmokers also had declines with work-years when compared to a nonsmoking comparison population. Nonsmokers with personal dust measurements had a significant decline of FEV1.0 related to respirable dust exposure. A shift study of 104 workers revealed a significant fall in FEV1.0 among nonsmokers and surface workers. Significance was approached in the high dust exposure group. An increase in the mean percent predicted forced vital capacity and FEV1.0 was shown for the 125 workers who had a 5-yr follow-up of pulmonary function. There was no correlation between the shift study decrements and the longitudinal 5-yr follow-up. Industrial hygiene dust sampling found elevated levels of total dust but lower respirable dust, with no detectable free silica.     

Loss of lung function associated with exposure to silica dust and with smoking and its relation to disability and mortality in South African gold miners.

The data from a lung function study on 2209 white 45-54 year old South African gold miners in 1968-71 and at a five year follow up examination, were analysed to establish the actual loss of lung function associated with exposure to silica dust and with smoking. Ex-smokers were excluded from the analysis. Of the remaining 1625 subjects, 1249 had the five year follow up test of lung function. The estimated excess loss of lung function for a 50 year old gold miner, associated with 24 years of underground dust exposure of an average respirable dust concentration of 0.30 mg m-3 (14.4 ghm-3) was 236 ml of FEV1 (95% confidence interval (95% CI 134-337) and 217 ml of FVC (95% CI 110-324). By comparison, the effect of smoking one packet of cigarettes a day over 30 years was associated with an estimated loss of 552 ml of FEV1 (95% CI 461-644) and 335 ml of FVC (95% CI 170-500). The cumulative dust exposure was not associated with the longitudinal loss of FEV1 or FVC when the initial FEV1 and FVC were adjusted in the models. According to the predicted values, however, gold miners appear to have a greater loss of lung function from 50 to 55 years of age than that predicted for a general population.     

Loss of lung function associated with exposure to silica dust and with smoking and its relation to disability and mortality in South African gold miners.

The data from a lung function study on 2209 white 45-54 year old South African gold miners in 1968-71 and at a five year follow up examination, were analysed to establish the actual loss of lung function associated with exposure to silica dust and with smoking. Ex-smokers were excluded from the analysis. Of the remaining 1625 subjects, 1249 had the five year follow up test of lung function. The estimated excess loss of lung function for a 50 year old gold miner, associated with 24 years of underground dust exposure of an average respirable dust concentration of 0.30 mg m-3 (14.4 ghm-3) was 236 ml of FEV1 (95% confidence interval (95% CI 134-337) and 217 ml of FVC (95% CI 110-324). By comparison, the effect of smoking one packet of cigarettes a day over 30 years was associated with an estimated loss of 552 ml of FEV1 (95% CI 461-644) and 335 ml of FVC (95% CI 170-500). The cumulative dust exposure was not associated with the longitudinal loss of FEV1 or FVC when the initial FEV1 and FVC were adjusted in the models. According to the predicted values, however, gold miners appear to have a greater loss of lung function from 50 to 55 years of age than that predicted for a general population.     

An 11-year longitudinal study of the occupational dust exposure and lung function of polyvinyl chloride, cement and asbestos cement factory workers

Standardized questionnaires and lung function tests were administered in 1973, 1980, and 1984 to 126 workers occupationally exposed to polyvinyl chloride (PVC) dust, to cement dust, or to asbestos cement dust until 1974-1978 and to PVC thereafter. The workers in the last group were assigned to two asbestos exposure categories (heavy and slight). The decline in forced vital capacity (FVC) and forced expiratory volume in 1 s (FEV1.0) was analyzed with regard to the length of time since the data of first employment. After adjustment for age, height, and smoking status at the date of first employment, the decline in FVC and FEV1.0 among the nonsmokers-light smokers was slightly accelerated with length of employment in the PVC and slight asbestos exposure groups and markedly accelerated with time since first employment in the heavy asbestos exposure group. The heavy smokers in all the exposure groups had FVC and FEV1.0 predicted values that were lower than those of the nonsmokers-light smokers; these differences remained constant with length of employment. Cessation of asbestos exposure for about 10 years did not seem to change lung function decline.     

Respiratory Status of Surface Coal Miners in the United States

The United States Public Health Service examined 1,438 surface coal miners to determine the prevalence of coal worker’s pneumoconiosis (CWP), chronic bronchitis, and ventilatory impairment among them. Four percent (fifty-nine individuals) showed some roentgenographic evidence of pneumoconiosis, but only seven miners had films interpreted as CWP of category2 or greater (according to the UlCC/Cincinnati classification system). Moreover, most of the affected miners had worked in underground coal mines for prolonged periods. Significant decrements in pulmonary function to increasing exposure to surface mine dust were demonstrated only in the forced vital capacity of smokers. Increased prevalence of chronic bronchitis with increasing exposure was found in all smoking categories. However, significant airway obstruction was an uncommon finding (6.6%) in nonsmoking miners. Employment in surface mining was not likely to cause either the development of CWP or clinically significant respiratory impairment.     

Ventilatory function and personal breathing zone dust concentrations in Lancashire textile weavers

BACKGROUND: To report findings on ventilatory function and estimations of concentrations of personal breathing zone dust in Lancashire textile weavers. Weaving room dust is considered to be less harmful than that encountered in the cardroom or spinning room and weavers are generally thought to have less respiratory disability than carders or spinners. However, this occupational group has not been extensively studied. METHODS: Each person was given a respiratory symptom questionnaire (modified Medical Research Council, UK, questionnaire on respiratory diseases). Ventilatory function tests, forced expiratory volume in 1 second (FEV1) and forced vital capacity (FVC) were performed on each person. A representative sample of workers from each occupational group underwent dust sampling in their personal breathing zone. Dust concentrations and ventilatory tests were analysed statistically with the Student's t test, Pearson's correlation coefficient, and forward step regression for relations with symptoms and environmental factors. Significance was p > or = 0.05. RESULTS: The FEV1 and FVC were reduced in workers with respiratory symptoms (non-specific chest tightness, shortness of breath, persistent cough, and wheezing) as well as in preparation room workers, current and former smokers, Asians, those working with predominantly cotton fibre (> 50% cotton) and starch size. Mean total dust concentration (pd1) in the personal breathing zone was 1.98 mg/m3. The corresponding value for total dust with large fibres lifted off the filter paper (pd2) was 1.55 mg/m3. There was a strong correlation (r = 0.94, p < 0.0001) between pd1 and pd2. Non-specific chest tightness was predicted by low dust concentrations and persistent cough by high dust concentrations. On regression analysis, impairment of ventilatory function (FEV1, FVC) was predicted by smoking, male sex, age, not working in the weaving shed, not being white, and personal dust concentrations. CONCLUSIONS: The FEV1 and FVC were impaired in smokers and those exposed to high dust concentrations in the personal breathing zone. Symptoms were inconsistently related to dust concentrations in the personal breathing zone.